This invention relates to the stabilization of hydrocarbons against light-induced sedimentation. The invention is particularly directed to additives useful in preventing or resisting hydrocarbon degradation due to exposure to actinic energy, and is more particularly directed to the stabilization of hydrocarbon liquids which have been subjected to hydroprocessing. Most particularly, the invention is directed to stabilizing base lubricating oils and fuel oils obtained from hydroprocessed feedstocks, and especially from hydroprocessed shale oils or fractions thereof.
It has been the practice to prepare lubricating oils and fuel oils from various hydrocarbon crude sources by fractional distillation. More recently, lubricating oils have been produced by hydroprocessing crude oils and distilling the resulting product. Unfortunately, lubricating oil fractions produced by hydroprocessing suffer from a shortcoming in that they are unstable when exposed to light. Specifically, when exposed to sunlight or ultraviolet radiation, a brown precipitate forms. Such a precipitate is undesirable, not only because it may prove detrimental to the lubrication function which the oil is to perform, but also because it reduces the aesthetic value of what would otherwise be a clear premium quality oil.
The patent literature has recognized the need to stabilize hydrocarbon compositions with respect to reaction-inducing environmental factors. U.S. Pat. No. 3,671,423 issued to MacDonald et al. discloses stabilizing lubricating oils to light and air by percolating the oil through silica-alumina gels containing a Y-type molecular sieve. U.S. Pat. No. 3,781,196 issued to Thompson discloses a process for the production of a stabilized lubricant oil by serially extracting a hydrocracked lube oil with furfural. U.S. Pat. No. 4,264,461 issued to Chao et al. discloses a process for stabilizing hydrocracked lubricating oils to deterioration induced by light by the addition of certain substantially aliphatic amine components.
Presently, the conversion to alternative energy sources has increased the need to prevent light-induced sediment formation. Shale oil is one of the most promising alternative sources of energy for the future. Yet, the chemical and physical nature of shale oil mandates that it be subjected to hydroprocessing, resulting in products severely limited in usefulness due to rapid formation of sediment. The acuteness of the sedimentation problem is demonstrated by the fact that a typical hydroprocessed syncrude derived from shale oil forms a noticeable sediment upon exposure to sunlight within just two days.
The problems caused by this rapid, light-induced sediment formation are manifold. In a lubricating oil a drastic deterioration results, so as to shorten the useful life of the oil. Similarly, fuels such as automotive gasoline derived from shale oil syncrude rapidly form sediment upon exposure to light. Such sediments severely foul the mechanical elements of an internal combustion engine and contribute to preignition, cause valve burning, and tend to increase octane requirements.
In view of the foregoing, one object of this invention is to inhibit or prevent light-induced sediment formation in hydroprocessed liquid hydrocarbons.
Another object of this invention is to stabilize shale oil-derived hydroprocessed liquid hydrocarbons to light-induced sediment formation.
Another object of this invention is to stabilize lubricating oils produced by hydroprocessing against light-induced sediment formation.
Yet another object of this invention is to stabilize fuel oils produced by hydroprocessing against light-induced sediment formation.
These and other objects and advantages of the invention will become apparent in view of the following description of the invention.